JP2014172328A - Liquid droplet discharge head, liquid cartridge, and image formation apparatus - Google Patents

Abstract

An adhesive for bonding a holding substrate and a piezoelectric element substrate is prevented from flowing out onto a diaphragm.
A droplet discharge head includes a nozzle substrate 30 having nozzle holes 31, a liquid chamber 21a communicating with the nozzle holes 31, a flow path forming layer 21 having a partition wall of the liquid chamber 21a, and a part of a wall surface of the liquid chamber 21a. And a piezoelectric element substrate 20 having a piezoelectric element 23 disposed on the surface opposite to the liquid chamber 21a of the diaphragm 22, and a gap 12 is formed in a portion facing the piezoelectric element 23. And a holding substrate 10 bonded to the substrate 20 with an adhesive. The piezoelectric element substrate 20 includes a convex bonding portion 25 having a plurality of steps on the side surface at a position where the holding substrate 10 is bonded.
[Selection] Figure 1

Description

  The present invention relates to a droplet discharge head, a liquid cartridge, and an image forming apparatus.

  Many image forming apparatuses such as printers and copiers adopt an ink jet system. In an inkjet head, image resolution is increased by narrowing the pitch between nozzles. Therefore, a droplet discharge head has been developed by adopting MEMS (Micro Electro Mechanical Systems) technology applying a semiconductor process.

  As an ink-jet driving method, an electromechanical conversion method using a piezoelectric element is often used. In this method, the displacement of the piezoelectric element is transmitted to the diaphragm so that the pressure in the liquid chamber is changed and ink droplets are ejected.

  In this method, an actuator substrate (piezoelectric element substrate) in which a piezoelectric element, a diaphragm and a liquid chamber are integrally formed by MEMS technology, a subframe substrate (holding substrate) that reinforces the substrate, a nozzle substrate in which nozzle holes are formed, and the like. The method of bonding is common. When the actuator substrate and the sub-frame substrate, or the actuator substrate and the nozzle substrate are bonded together, it is a commonly used technique to perform bonding using a resin such as an adhesive.

FIG. 9 is a schematic cross-sectional view for explaining a conventional droplet discharge head.
The droplet discharge head includes a subframe substrate 10, an actuator substrate 20, and a nozzle substrate 30.
The subframe substrate 10 includes a partition wall 11 and a recess 12. The partition wall portion 11 is a portion that becomes a joint portion with the actuator substrate 20. The recess 12 is for providing a gap on the diaphragm of the actuator substrate 20.

  The actuator substrate 20 includes a flow path forming layer 21, a diaphragm 22, a piezoelectric element 23, and a joint portion 26. The flow path forming layer 21 includes a liquid chamber 21a and a partition wall 21b. The diaphragm 22 constitutes one wall surface of the liquid chamber 21a.

  The piezoelectric element 23 is formed by laminating a lower electrode layer 23a, a piezoelectric layer 23b, and an upper electrode layer 23c on the diaphragm 22 in that order. The piezoelectric element 23 is covered with an interlayer insulating film 24.

  The joint portion 26 is a portion to which the partition wall portion 11 of the subframe substrate 10 is joined. The joint portion 26 has a convex shape. The joint portion 26 is formed of a metal wiring 26a and a protective film 26b that covers the metal wiring 26a.

  The nozzle substrate 30 includes nozzle holes 31. The nozzle hole 31 is for discharging the liquid in the liquid chamber 21a, and is disposed at a position corresponding to the liquid chamber 21a.

  The partition wall portion 11 of the subframe substrate 10 is bonded to the bonding portion 26 of the actuator substrate 20 with an adhesive 40. The nozzle substrate 30 is bonded to the partition wall 21a of the actuator substrate 20 with an adhesive (not shown).

  When a predetermined voltage is applied to the lower electrode 23a and the upper electrode 23c of the piezoelectric element 23, the piezoelectric layer 23b expands and contracts, and the diaphragm 22 is displaced. As a result, the volume of the liquid chamber 21 a is displaced, and ink is ejected from the liquid chamber 21 a through the nozzle hole 31.

  When the partition wall portion 11 of the subframe substrate 10 and the joint portion 26 of the actuator substrate 20 are bonded, the adhesive 40 is applied to the partition wall portion 11 of the subframe substrate 10, for example. After the subframe substrate 10 and the actuator substrate 20 are aligned, the partition wall portion 11 and the joint portion 26 are brought into contact with and pressurized, and are heated to about 60 ° C., which is the crosslinking temperature of the adhesive 40, and cured. At this time, the adhesive 40 is temporarily softened from heating to curing, and excess adhesive 40 starts to flow out from the side surface of the joint portion 26 of the actuator substrate 20, and in some cases, flows to the diaphragm 22 or the piezoelectric element 23. After some time it hardened.

  When the flowed adhesive 40 is cured on the vibration plate 22 or the piezoelectric element 23, the cured adhesive 40 inhibits the displacement of the vibration plate 22 or the piezoelectric element 23, thereby causing variation in ink droplet ejection. There was a problem.

  The adhesive 40 is required to have a thickness of, for example, 1 μm (micrometer) or more from the viewpoint of securing adhesive strength and reducing the influence of foreign matter contamination. Further, as described above, since the pitch between the bits of the nozzle holes 31 is narrowed, the distance between the diaphragm 22 and the bonding surface of the subframe substrate 10 is often about several μm. Therefore, it is required that the excess adhesive 40 flow out to be several μm or less.

FIG. 10 is a schematic cross-sectional view for explaining another example of a conventional droplet discharge head.
The liquid droplet ejection head shown in FIG. 10 includes a convex structure 27 with the joint 26 interposed therebetween. The convex structure portion 27 is formed of a metal wiring 27a and a protective film 27b covering the metal wiring 27a. Such a structure is disclosed in Patent Document 1, for example.

  By the convex structure portion 27 disposed in the vicinity of the joint portion 26 with a space from the joint portion 26, an effect of blocking the flowing out adhesive 40 can be expected. If the convex structure portion 27 is formed on the diaphragm 22, the convex structure portion 27 becomes an obstruction factor for displacement of the diaphragm 22, and thus needs to be disposed on the partition wall 21 b. In this case, even if the convex structure portion 27 is formed with the minimum dimension of the process, it is necessary to increase the width dimension of the partition wall 21b in consideration of the space between the joint portion 26 and the convex structure portion 27. As the width dimension of the partition wall 21b increases, the pitch of the liquid chambers 21a increases.

  In general, in the case of a droplet discharge head, the number of nozzles, that is, the number of liquid chambers increases as the resolution increases. At present, there is also a droplet discharge head in which liquid chambers of 150 channels or more are formed in parallel. Therefore, widening the partition wall is not preferable because it greatly affects the chip size.

  An object of the present invention is to prevent an adhesive for joining a holding substrate and a piezoelectric element substrate from flowing out onto a vibration plate.

  A droplet discharge head according to the present invention includes a nozzle substrate having nozzle holes, a liquid chamber communicating with the nozzle holes, a flow path forming layer having partition walls of the liquid chambers, and vibrations forming part of the wall surfaces of the liquid chambers. And a piezoelectric element substrate having a piezoelectric element disposed on a surface opposite to the liquid chamber of the plate and the diaphragm, and a gap is formed in a portion facing the piezoelectric element, and is bonded to the piezoelectric element substrate with an adhesive. The piezoelectric element substrate is characterized in that a convex bonding portion having a plurality of steps on the side surface is provided at a portion to which the holding substrate is bonded.

  The droplet discharge head according to the present invention includes a convex joint having a plurality of steps on the side surface at a portion where the holding substrate is joined in the piezoelectric element substrate, so that the holding substrate and the piezoelectric element substrate are joined. Therefore, it is possible to prevent the adhesive for making it flow out onto the diaphragm.

It is a schematic sectional view for explaining an embodiment of a droplet discharge head. It is a schematic exploded perspective view of the same Example. FIG. 3 is a schematic cross-sectional view for explaining an example of a process for forming the liquid ejection head shown in FIGS. 1 and 2. FIG. 4 is a schematic cross-sectional view for explaining an example of a process for forming the liquid ejection head shown in FIGS. 1 and 2, for explaining a process subsequent to FIG. 3. FIG. 5 is a schematic cross-sectional view for explaining an example of a process for forming the liquid ejection head shown in FIGS. 1 and 2, and is a view for explaining a process subsequent to FIG. 4. It is a schematic perspective view for demonstrating one Example of a liquid cartridge. 1 is a schematic perspective view for explaining an embodiment of an image forming apparatus. It is a side view for demonstrating the mechanism part of the Example. It is a schematic sectional drawing for demonstrating the conventional droplet discharge head. It is a schematic sectional drawing for demonstrating the other example of the conventional droplet discharge head.

In the droplet discharge head of the present invention, an example of the adhesive has a contact angle of 30 degrees or more with respect to the surface of the joint. Another example of the adhesive is one having a loss elastic modulus of 1.2 × 10 ⁸ Pa or less (at 40 ° C.) and 2.0 × 10 ⁸ Pa or less (at 60 ° C.). The adhesive may have both of these characteristics. If such an adhesive is used, the adhesive flowing out from the joint surface between the holding substrate and the joint is likely to stay at the level difference of the joint, and the adhesive can be further prevented from flowing onto the diaphragm. However, in the droplet discharge head of the present invention, the adhesive is not limited to one having the above characteristics.
The loss elastic modulus is a component of loss energy (diffused as heat or the like outside the object) when strain occurs in the object, and the smaller this value, the more the material can be handled as an elastic body.

  In the liquid droplet ejection head according to the aspect of the invention, the convex shape of the joint portion may include a part or all of the material constituting the piezoelectric element, an interlayer insulating film, a wiring material, a wiring protective film, and a part of the diaphragm. Or the example currently formed by all the combinations can be given. According to this aspect, since the convex shape of the joint portion can be formed simultaneously with the formation of each component of the piezoelectric element substrate, an increase in the manufacturing process can be prevented.

  The liquid cartridge according to the present invention is a liquid cartridge in which a liquid droplet ejection head that ejects liquid droplets and a liquid tank that supplies liquid to the liquid droplet ejection head are integrated, and the liquid droplet ejection head is a liquid cartridge according to the present invention. It is a droplet discharge head. Since the liquid cartridge of the present invention includes the droplet discharge head of the present invention, it is possible to prevent the adhesive from flowing out to the diaphragm, improving the reliability of the droplet discharge head, and thus the reliability of the entire liquid cartridge. Can be improved.

  An image forming apparatus according to the present invention is an image forming apparatus provided with a droplet discharge head for discharging droplets, and the droplet discharge head is the droplet discharge head of the present invention. Since the image forming apparatus of the present invention includes the droplet discharge head of the present invention, the adhesive is prevented from flowing out to the vibration plate, and the reliability of the droplet discharge head is improved. Reliability can be improved.

  An embodiment of the present invention will be described. The present invention has the following characteristics regarding the bonding of the actuator substrate (piezoelectric element substrate) and the subframe substrate (holding substrate) of the droplet discharge head.

  In describing an embodiment of the present invention, the structure of an inkjet head manufactured using MEMS technology will be briefly described. An inkjet head, which is an example of a droplet discharge head, includes an actuator substrate, a subframe substrate, and a nozzle substrate. The actuator substrate and the sub-frame substrate, and the actuator substrate and the nozzle substrate are bonded to each other with an adhesive.

  The actuator substrate is integrally formed with a liquid chamber for storing ink, a thin diaphragm capable of moving one wall, and a piezoelectric element for driving the diaphragm. The drive of the piezoelectric element is transmitted to the diaphragm, and the volume of the liquid chamber is changed, whereby ink droplets are ejected from the liquid chamber.

  Since the thickness of the actuator substrate is greatly related to the volume of the liquid chamber, it is reduced to, for example, about several tens of μm. Therefore, a subframe substrate is attached to the actuator substrate for reinforcement. In the subframe substrate, a recess is formed at a position facing the piezoelectric element so that the piezoelectric element and the diaphragm portion displaced by the piezoelectric element are not bonded to the subframe substrate.

  The liquid chambers of the actuator substrate are formed in parallel by the number of bits of the nozzle holes, and adjacent diaphragms are densely present. The subframe substrate is bonded to the partition between the diaphragms by an adhesive so as not to inhibit the displacement of the diaphragms. When this adhesive flows onto the diaphragm, the displacement of the diaphragm is hindered, causing variations in ink ejection.

  In the droplet discharge head of the present invention, the actuator substrate is provided with a convex joint portion having a plurality of steps on the side surface at a position where the subframe substrate is bonded. The head can stop the flow of the adhesive at the step portion on the side surface of the joint.

  For example, the convex joints may be patterned simultaneously with the same material when, for example, a liquid chamber, a piezoelectric element, an electrode, or the like is formed in the actuator substrate forming process. Thereby, since an additional process is not required, an increase in manufacturing cost is prevented. In addition, this junction part may be formed including a dedicated material and process.

  In addition, when a dike-like convex wall is separately formed on the side of the joint (see, for example, Patent Document 1), the convex wall can be formed only with the minimum dimension of the process. The influence of is great. On the other hand, in the present invention, it is possible to form multi-steps on the side surfaces of the joint portion with a slight increase in dimensions, for example, the minimum dimension +1 μm, +2 μm,. Therefore, the present invention can reduce the influence on the entire chip design.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view for explaining an embodiment of a droplet discharge head. FIG. 2 is a schematic exploded perspective view of this embodiment.

The droplet discharge head includes a subframe substrate (holding substrate) 10, an actuator substrate (piezoelectric element substrate) 20, and a nozzle substrate 30.
The subframe substrate 10 includes a partition wall 11 and a recess 12. The partition wall portion 11 is a portion that becomes a joint portion with the actuator substrate 20. The recess 12 is for providing a gap on the piezoelectric element 23 so that the subframe substrate 10 does not contact the piezoelectric element 23 of the actuator substrate 20.

  The actuator substrate 20 includes a flow path forming layer 21, a vibration plate 22, a piezoelectric element 23, an interlayer insulating film 24, and a joint portion 25.

  The flow path forming layer 21 includes a liquid chamber 21a and a partition wall 21b. The liquid chamber 21a is a space in which the discharged liquid is stored. The partition wall 21b constitutes a side surface of the liquid chamber 21a and demarcates the formation position of the liquid chamber 21a.

  The diaphragm 22 is disposed on the liquid chamber 21a and the partition wall 21b of the flow path forming layer 21. The diaphragm 22 is formed of a plurality of layers such as a silicon oxide layer, a silicon nitride layer, and a polysilicon layer, for example. The diaphragm 22 constitutes one wall surface of the liquid chamber 21a.

  The piezoelectric element 23 is formed by laminating a lower electrode layer 23a, a piezoelectric layer 23b, and an upper electrode layer 23c on the diaphragm 22 in that order. The piezoelectric layer 23b is formed of, for example, a PZT (lead zirconate titanate) film.

  The interlayer insulating film 24 is formed on the vibration plate 22 so as to cover the piezoelectric element 23. The interlayer insulating film 24 functions as a protective film for the piezoelectric element 23.

  The joint portion 25 is disposed on the interlayer insulating film 24 where the partition wall portion 11 of the subframe substrate 10 is joined. The joint portion 25 has a convex shape having a plurality of steps on the side surface. The joint portion 25 includes a lower electrode layer 25a, a piezoelectric layer 25b, an upper electrode layer 25c, an interlayer insulating film 25d, a metal wiring 25e, and a protective film 25f. The joint portion 25 is disposed above the partition wall 21 b of the flow path forming layer 21 so as not to hinder the displacement of the diaphragm 22 due to the driving of the piezoelectric element 23.

  The lower electrode layer 25a is formed of the same material as that of the lower electrode layer 23a of the piezoelectric element 23 at the same time.

  The piezoelectric layer 25b is formed of the same material as that of the piezoelectric layer 23b of the piezoelectric element 23 at the same time. The piezoelectric layer 25b is formed on the lower electrode layer 25a with a width dimension smaller than the width dimension of the lower electrode layer 25a. Thereby, a step is formed on the side surface of the stacked body of the lower electrode layer 25a and the piezoelectric layer 25b.

  The upper electrode layer 25c is formed of the same material as that of the upper electrode layer 23c of the piezoelectric element 23 at the same time. The upper electrode layer 25c is formed on the piezoelectric layer 25b with a width dimension smaller than the width dimension of the piezoelectric layer 25b. Thereby, a step is formed on the side surface of the laminate of the piezoelectric layer 25b and the upper electrode layer 25c.

  The interlayer insulating film 25d is formed of the same material as the interlayer insulating film 24 covering the piezoelectric element 23 at the same time. The interlayer insulating film 25d covers the stacked body of the lower electrode layer 25a, the piezoelectric layer 25b, and the upper electrode layer 25c. Due to the step existing on the side surface of the stacked body, three steps are formed on the side surface of the interlayer insulating film 25d.

  The metal wiring 25e is formed simultaneously with the same material as the metal wiring (not shown) for taking the potential of the lower electrode layer 23a and the upper electrode layer 23c of the piezoelectric element 23. The metal wiring 25e is formed on the interlayer insulating film 25d with a width dimension smaller than the width dimension of the upper end surface of the interlayer insulating film 25d.

  The protective film 25f is a protective film (not shown) formed so as to cover the metal wiring (not shown) for taking the potential of the lower electrode layer 23a and the upper electrode layer 23c of the piezoelectric element 23. (Omitted) and the same material. The protective film 25f covers the metal wiring 25e.

  The side surface of the base end portion (the portion disposed on the upper end surface of the interlayer insulating film 25d) of the interlayer insulating film 25d is disposed on the side surface side of the interlayer insulating film 25d with respect to the upper end surface of the protective film 25f. Thereby, a step is formed on the side surface of the interlayer insulating film 25d.

The base end portion of the protective film 25f is disposed at a position spaced from the side surface of the interlayer insulating film 25d. Thereby, a step is formed between the side surface of the protective film 25f and the side surface of the interlayer insulating film 25d.
Thus, a total of five steps are formed on the side surface of the joint portion 25.

  The nozzle substrate 30 includes nozzle holes 31. The nozzle hole 31 is for discharging the liquid in the liquid chamber 21a, and is disposed at a position corresponding to the liquid chamber 21a.

  The partition wall portion 11 of the subframe substrate 10 is bonded to the bonding portion 25 of the actuator substrate 20 with an adhesive 40. The nozzle substrate 30 is bonded to the partition wall 21a of the actuator substrate 20 with an adhesive (not shown).

  When a predetermined voltage is applied to the lower electrode 23a and the upper electrode 23c of the piezoelectric element 23, the piezoelectric layer 23b expands and contracts, and the diaphragm 22 is displaced. As a result, the volume of the liquid chamber 21 a is displaced, and ink is ejected from the liquid chamber 21 a through the nozzle hole 31. Since the joining portion 25 is formed in a region facing the partition wall 21b of the flow path forming layer 21, that is, a region where the vibration plate 22 is not displaced, the vibration plate 22 caused by driving the piezoelectric element 23 inhibits displacement. There is no.

  In this embodiment, a plurality of steps are formed on the side surface of the joint portion 25. When the subframe substrate 10 and the actuator substrate 20 are joined, even if excess adhesive 40 flows out to the side surface of the joint portion 25, the flowed adhesive 40 remains at the inflection point of the step on the side surface of the joint portion 25. Try to stay at. Even if surplus adhesive 40 flows out beyond the first step, the adhesive 40 tries to stay at the next step. Thereby, this embodiment can prevent excess adhesive 40 from flowing out onto the diaphragm 22. Therefore, this embodiment can improve the reliability of the droplet discharge head.

  In this embodiment, each member constituting the joint portion 25 is formed simultaneously with patterning of each member of the vibration plate 22, the interlayer insulating film 24, the metal wiring (not shown), and the piezoelectric element 23 when the actuator substrate 20 is formed. Is done. Therefore, only a design change is required and no additional process is required.

  Further, regarding the design, since the convex shape of the joint portion 25 is made slightly larger than the dimension of the partition wall portion 11 of the subframe substrate 10, the joint portion 25 is not limited by the minimum rule of the process. Can be formed. Therefore, a significant increase in the pitch of the liquid chamber 21a can be suppressed.

  Note that a pattern similar to that of the bonding portion 25 may be formed on a bonding surface of a penetrating portion provided in the droplet discharge head such as an ink supply hole (not shown). In this case, the amount of excess adhesive can be determined quantitatively by confirming to which step the adhesive 40 has flowed from the upper end surface of the joint portion 25. Thereby, it can be expected to simplify the inspection of the process management of the adhesive bonding process.

  3, 4, and 5 are schematic cross-sectional views for explaining an example of a process for forming the liquid discharge head shown in FIGS. 1 and 2. With reference to FIG. 3, FIG. 4 and FIG. 5, an example of this forming process will be described. The parentheses for each step described below correspond to the parentheses in FIGS. 3, 4, and 5.

(1) In order to form the actuator substrate 20, the diaphragm 22 is formed on the flow path forming layer 21. The flow path forming layer 21 is, for example, a silicon substrate having a thickness of 625 μm and a plane orientation of <100>. A vibration plate 22 is formed by forming a silicon oxide film, a silicon nitride film, and a polysilicon film in desired thicknesses on the flow path forming layer 21 by a thermal oxidation method and a CVD (chemical vapor deposition) method.

(2) On the vibration plate 22, a lower electrode layer 51a, a piezoelectric layer 51b, and an upper electrode layer 51c for forming the piezoelectric element 23 and the joint portion 25 are formed in that order. The lower electrode layer 51a is, for example, a stacked film of SrRuO ₃ (SRO) film / Pt film / Ti film sequentially formed by sputtering. The piezoelectric layer 51b is a PZT film formed by a sol-gel method, for example. The upper electrode layer 51c is, for example, a laminated film of SRO film / Pt film sequentially formed by sputtering.

(3) The upper electrode layer 51c is patterned by photolithography and etching techniques to form the upper electrode layer 23c of the piezoelectric element 23 and the upper electrode layer 25c of the joint portion 25. The upper electrode layer 23c and the upper electrode layer 25c are patterns that are electrically separated from each other.

(4) The piezoelectric layer 51b is patterned by photolithography and etching techniques to form the piezoelectric layer 23b of the piezoelectric element 23 and the piezoelectric layer 25b of the joint portion 25. The piezoelectric layer 23b and the piezoelectric layer 25b are patterns that are electrically separated from each other. The piezoelectric layer 25b is formed under the upper electrode layer 25a with a width dimension larger than the width dimension of the upper electrode layer 25a. The side surface of the upper electrode layer 25c is disposed at a position spaced from the side surface of the piezoelectric layer 25b.

(5) The lower electrode layer 51a is patterned by photolithography and etching techniques to form the lower electrode layer 23a of the piezoelectric element 23 and the lower electrode layer 25a of the joint 25. Thereby, the piezoelectric element 23 formed by laminating the lower electrode layer 23a, the piezoelectric layer 23b, and the upper electrode layer 23c is formed.

  The lower electrode layer 23a and the lower electrode layer 25a are patterns that are electrically separated from each other. The lower electrode layer 25a is formed under the piezoelectric layer 25b with a width dimension larger than the width dimension of the piezoelectric layer 25b. The side surface of the lower electrode layer 25a is disposed at a position spaced from the side surface of the piezoelectric layer 25b.

  As described above, in the laminated body of the lower electrode layer 25a, the piezoelectric body layer 25b, and the upper electrode layer 25c, the pattern of each layer is increased in order toward the lower layer side, so that multi-steps are formed on the side surface of the laminated body. Designed to be.

  In this formation process example, the upper electrode layer 51c, the piezoelectric layer 51b, and the lower electrode layer 51a are separately patterned. However, for example, the upper electrode layer 51c and the piezoelectric layer 51b, or the piezoelectric layer 51b and the lower electrode layer 51a may be patterned at once using the same mask pattern.

(6) The interlayer insulating film 24 is formed. The interlayer insulating film 24 covers the piezoelectric element 23 and the laminate of the lower electrode layer 25a, the piezoelectric layer 25b, and the upper electrode layer 25c. The interlayer insulating film 24 is formed, for example, with a two-layer structure made of a laminate of an Al ₂ O ₃ film formed by ALD (Atomic Layer Deposition) method and a silicon oxide film formed by CVD method. The portion of the interlayer insulating film 24 that covers the laminated body of the lower electrode layer 25a, the piezoelectric layer 25b, and the upper electrode layer 25c constitutes the interlayer insulating film 25d of the bonding portion 25.

(7) A metal wiring (not shown) for transmitting an external signal to the piezoelectric element 23 and a metal wiring 25e of the joint portion 25 are simultaneously formed of the same material. The external signal metal wiring and the metal wiring 25e are formed by, for example, forming a laminated film of an Al film / TiN film by a sputtering method and then patterning the film by a photolithography technique and an etching technique.

  A passivation film is formed, and the passivation film is patterned to simultaneously form a protective film that covers the external signal metal wiring and a protective film 25f that covers the metal wiring 25e. The protective film 25f is disposed on the interlayer insulating film 25d. A step is formed on the side surface of the protective film 25f.

  As a result, a junction 25 is formed in which the lower electrode layer 25a, the piezoelectric layer 25b, the upper electrode layer 25c, the interlayer insulating film 25d, the metal wiring 25e, and the protective film 25f are laminated in this order from the lower layer side.

  1, 2, 4, and 5, the external signal metal wiring connected to the upper electrode layer 23 c of the piezoelectric element 23 and the external signal metal wiring connected to the lower electrode layer 23 a are illustrated. It is omitted. In practice, the metal wiring 25e and these external signal metal wirings are partially connected, and the electrical signal is designed to be transmitted to the upper electrode layer 23c and the lower electrode layer 23a, respectively. The metal wiring 25e electrically connected to the upper electrode layer 23c and the metal wiring 25e electrically connected to the lower electrode layer 23a are insulated from each other.

(8) The actuator substrate 20 and the subframe substrate 10 are bonded together. The subframe substrate 10 includes a partition wall portion 11 joined to the joint portion 25 and a concave portion 12 serving as a gap on the piezoelectric element 23 formed by a photoengraving technique and an etching technique. Although not shown in FIGS. 1, 2, and 5, there may be a case where a through hole for mounting an ink supply hole, an IC for transmitting an external signal, or the like is formed in the subframe substrate 10.

  For example, the adhesive 40 is applied only to the back surface (surface facing the actuator substrate 20) of the partition wall 11 of the subframe substrate 10 by a printing technique. With the bonding apparatus, the actuator substrate 20 and the sub-frame substrate 10 are aligned, contacted and pressurized, and the temperature is raised to cure the adhesive 40. As the adhesive 40, for example, an adhesive that is cured at about 60 to 100 ° C. for several minutes is used. Due to the pressurization and temperature rise, excess adhesive 40 flows out to the side surface of the joint portion 25.

  In this example of forming process, a material having a relatively high viscosity of about 40 cp (centipoise) and a tendency for the flow of the adhesive 40 to stay at the inflection point of the step on the side surface of the joint portion 25 is selected as the adhesive 40. As a result, the excess adhesive 40 that has flowed out to the side surface of the joint portion 25 stays at the multi-steps formed on the side surface of the joint portion 25, and the excess adhesive agent 40 is prevented from flowing out to the diaphragm 22.

It is preferable that the adhesive 40 that easily flows out at the inflection point of the step on the side surface of the joint portion 25 has, for example, a contact angle with the surface of the joint portion 25 of 30 degrees or more. The adhesive 40 preferably has a loss elastic modulus of 1.2 × 10 ⁸ Pa or less (at 40 ° C.) and 2.0 × 10 ⁸ Pa or less (at 60 ° C.). The adhesive 40 preferably has both of these characteristics.

(9) The flow path forming layer 21 of the actuator substrate 20 is thinned by a polishing process. The flow path forming layer 21 is patterned by photolithography and etching techniques to form the liquid chambers 21a and the partition walls 21b. The thickness of the flow path forming layer 21 after polishing is adjusted to a desired value in accordance with the volume of the liquid chamber 21a.

  Finally, although not shown, the droplet discharge head forming process is completed by bonding the nozzle substrate 30 to the partition wall 21b with an adhesive.

  In this embodiment, the step on the side surface of the joint portion 25 is formed by the lower electrode layer 25a, the piezoelectric layer 25b, the upper electrode layer 25c, the interlayer insulating film 25d, the metal wiring 25e, and the protective film 25f. However, a step may be formed on the side surface of the joint portion 25 by using only a part of these members constituting the joint portion 25 depending on the characteristics of the adhesive 40, the coating film thickness, and the like.

  Further, as described above, for example, multi-steps may be formed at the joint portion at the portion where the subframe substrate 10 penetrates, such as the ink supply hole portion, similarly to the side surface of the joint portion 25. In this case, it is possible to easily inspect the amount of excess adhesive by observing from the upper surface and confirming to what level the adhesive has flowed out.

FIG. 6 is a schematic perspective view for explaining an embodiment of the liquid cartridge.
The liquid cartridge 201 is obtained by integrating the droplet discharge head 203 of the above-described embodiment having the nozzle holes 202 and the like, and the liquid tank 204 that supplies liquid to the droplet discharge head 203.

  Thus, in the case of the liquid tank integrated head, the performance of the droplet discharge head 203 immediately leads to the performance of the entire liquid cartridge 201. Therefore, by using the highly reliable droplet discharge head 203, the reliability is high. A liquid cartridge 201 can be obtained.

  FIG. 7 is a schematic perspective view for explaining an embodiment of the image forming apparatus. FIG. 8 is a side view for explaining the mechanism of this embodiment.

  The image forming apparatus 301 houses a printing mechanism unit 303 and the like inside a recording apparatus main body 302. The printing mechanism 303 includes a carriage 310 that can be moved in the main scanning direction, a recording head 311 that is a droplet discharge head that is mounted on the carriage 310 and embodies the present invention, an ink cartridge 312 that supplies ink to the recording head 311, and the like. Has been. In the lower part of the recording apparatus main body 302, the image forming apparatus 301 can be detachably mounted with a paper feed cassette (or a paper feed tray) 305 capable of stacking a large number of sheets 304 from the front side. Further, the image forming apparatus 301 can open the manual feed tray 306 for manually feeding the paper 304. The image forming apparatus 301 takes in the paper 304 fed from the paper feed cassette 305 or the manual feed tray 306, records a required image by the printing mechanism unit 303, and then discharges the paper onto a paper discharge tray 307 mounted on the rear side. To do.

  The printing mechanism section 303 holds the carriage 310 slidably in the main scanning direction (perpendicular to the paper surface in FIG. 8) with a main guide rod 308 and a sub guide rod 309, which are guide members horizontally mounted on left and right side plates (not shown). doing. The carriage 310 includes a recording head including a droplet discharge head according to the present invention that discharges yellow (Y), cyan (C), magenta (M), and black (Bk) ink droplets. Nozzles) are arranged in a direction crossing the main scanning direction. The recording head is mounted with the ink droplet ejection direction facing downward. In addition, each ink cartridge 312 for supplying ink of each color to the recording head is replaceably mounted on the carriage 310.

  The ink cartridge 312 has an air port that communicates with the atmosphere above, and a supply port that supplies ink to the inkjet head below. In addition, the ink cartridge 312 has a porous body filled with ink, and the ink supplied to the inkjet head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the recording heads of the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 310 is slidably fitted to the main guide rod 308 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 309 on the front side (upstream side in the paper conveyance direction). It is location. In order to move and scan the carriage 310 in the main scanning direction, a timing belt 316 is stretched between a driving pulley 314 and a driven pulley 315 that are rotationally driven by a main scanning motor 313. The carriage 310 is fixed to the timing belt 316, and the carriage 310 is reciprocated by forward and reverse rotation of the main scanning motor 313.

  In order to convey the sheet 304 set in the sheet feeding cassette 305 to the lower side of the recording head, a sheet feeding roller 317, a friction pad 318, a guide member 319, a conveying roller 320, a conveying roller 321 and a leading end roller 322 are provided. . A paper feed roller 317 and a friction pad 318 separate and feed the paper 304 from the paper feed cassette 305. A guide member 319 guides the sheet 304. The conveyance roller 320 inverts and conveys the fed sheet 304. The conveyance roller 321 is pressed against the peripheral surface of the conveyance roller 320. The leading end roller 322 defines the feed angle of the sheet 304 from the transport roller 320. The conveyance roller 320 is rotationally driven by a sub-scanning motor 323 through a gear train.

  A printing receiving member 324 is provided as a paper guide member for guiding the paper 304 fed from the conveying roller 320 below the recording head 311 corresponding to the range of movement of the carriage 310 in the main scanning direction. On the downstream side of the printing receiving member 324 in the sheet conveyance direction, a conveyance roller 325 and a spur 326 that are rotationally driven to send out the sheet 304 in the sheet discharge direction are provided. Further, a paper discharge roller 327 and a spur 328 for sending the paper 304 to the paper discharge tray 307, and guide members 329 and 330 for forming a paper discharge path are provided.

  At the time of recording, the recording head 311 is driven according to the image signal while moving the carriage 310 to eject ink onto the stopped paper 304 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 304 has reached the recording area, the recording operation is terminated and the sheet 304 is discharged.

  A recovery device 331 for recovering the ejection failure of the recording head is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 310. The recovery device 331 includes a cap unit, a suction unit, and a cleaning unit. The carriage 310 is moved to the recovery device 331 side during printing standby, and the recording head is capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  In case of ejection failure, etc., the ejection port (nozzle) of the recording head is sealed with a capping unit, air bubbles are sucked out together with ink from the ejection port with a suction unit through the tube, and ink or dust adhered to the ejection port surface Is removed by the cleaning means to recover the ejection failure. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, the image forming apparatus 301 includes the recording head 311 including the droplet discharge head embodying the present invention. Since the performance of the recording head 311 immediately leads to the overall performance of the image forming apparatus 301, the highly reliable image forming apparatus 301 can be obtained by using the highly reliable recording head 311 including the droplet discharge head embodying the present invention. Can be obtained.

  Note that the image forming apparatus according to the present invention can also be applied to a printer, a facsimile machine, a copying machine, a complex machine of these, and the like. The image forming apparatus according to the present invention is also applied to a liquid droplet discharge head or liquid droplet discharge apparatus that discharges a liquid other than ink, such as a DNA sample, a resist, or a pattern material, or an image forming apparatus that includes these. be able to.

  As mentioned above, although the Example of this invention was described, the numerical value, material, arrangement | positioning, number, etc. in the said Example are examples, This invention is not limited to these, It was described in the claim Various modifications are possible within the scope of the present invention.

  For example, in the above-described embodiment, five steps are formed on the side surface of the joint portion 25. However, in the droplet discharge head of the present invention, there are no particular limitations as long as the step portion on the side surface of the joint portion is two steps or more.

  The droplet discharge head of the present invention is not limited to the configuration of the droplet discharge head of the above embodiment. The droplet discharge head of the present invention can be applied to any configuration of droplet discharge head as long as the piezoelectric element substrate and the holding substrate are bonded together with an adhesive.

  In the droplet discharge head of the present invention, a plurality of nozzle holes may be arranged in one liquid chamber.

31 Nozzle hole 30 Nozzle substrate 21a Liquid chamber 21b Partition wall 21 Flow path forming layer 22 Diaphragm 23 Piezoelectric element 20 Actuator substrate (piezoelectric element substrate)
10 Subframe substrate 12 Recessed portion (void)
25 Bonding portion 201 Liquid cartridge 203 Liquid droplet ejection head 301 Image forming apparatus

JP 2009-78534 A

Claims (6)

A nozzle substrate having nozzle holes;
The liquid chamber communicating with the nozzle hole and a flow path forming layer having a partition wall of the liquid chamber, a vibration plate constituting a part of the wall surface of the liquid chamber, and a surface of the vibration plate opposite to the liquid chamber A piezoelectric element substrate having a piezoelectric element;
A gap formed in a portion facing the piezoelectric element, and a holding substrate bonded to the piezoelectric element substrate by an adhesive, and
The droplet discharge head according to claim 1, wherein the piezoelectric element substrate includes a convex bonding portion having a plurality of steps on a side surface at a position where the holding substrate is bonded.   The droplet discharge head according to claim 1, wherein the adhesive has a contact angle of 30 degrees or more with respect to the surface of the joint. 3. The droplet according to claim 1, wherein the adhesive has a loss elastic modulus of 1.2 × 10 ⁸ Pa or less (at 40 ° C.) and 2.0 × 10 ⁸ Pa or less (at 60 ° C.). Discharge head.   The convex shape of the joint portion is formed by a combination of a part or all of materials constituting the piezoelectric element, an interlayer insulating film, a wiring material, a wiring protective film, and a part or all of the diaphragm. The droplet discharge head according to any one of 1 to 3. In a liquid cartridge in which a droplet discharge head that discharges droplets and a liquid tank that supplies liquid to the droplet discharge head are integrated,
5. A liquid cartridge, wherein the droplet discharge head is the droplet discharge head according to any one of claims 1 to 4. In an image forming apparatus provided with a droplet discharge head for discharging droplets,
An image forming apparatus, wherein the droplet discharge head is the droplet discharge head according to claim 1.

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